1. Field of the Disclosure
The present disclosure relates to a method for performing offshore dry-docking services on a water-borne vessel, and, in particular, a Floating Production Storage and Offloading (FPSO) vessel while keeping mooring and riser systems connected.
2. Description of the Related Art
Water-borne monohull or multihull vessels require mandatory and incidental maintenance, repair, and inspection over their operational lifetimes. Some of these operations may require access to the part of the vessel that is normally submerged, such as the outer hull below the water line, propellers, sonar systems, seawater intakes, riser porches, etc. Some of these operations may be performed by divers; however, the time and expense of using divers may be high. Other operations are not performable unless the relevant sections of the vessel are removed from the water.
Numerous water-borne vessels are involved in time-sensitive and/or costly business endeavors, such as offshore refining/production/storage/drilling of petroleum. For example, Floating Production, Storage, and Offloading (FPSO) vessels are designed to receive hydrocarbons produced from nearby platforms or subsea template, process them, and store the hydrocarbons until they can be offloaded onto a tanker or transported through a pipeline. Typically, an FPSO is coupled to several wellheads on the bottom of the ocean.
The onshore dry-docking of a vessel in a port or harbor results in a loss of operating time or the cost of acquiring the services of a replacement vessel for the period of maintenance/repair and the time of travel to and from the dry-dock facility. For example, should the FPSO require repair or maintenance, the FPSO must be taken off line (closing the wellheads and removing the coupling lines) (i.e., the FPSO is in a non-operational state), and the FPSO is then directed to an onshore dry-dock. This prior method could cost operators millions of dollars in lost revenue as a result of a non-operational FPSO or having to obtain another FPSO to continue the production, processing and storage of hydrocarbons from the underwater formations. What is needed is a method of dry-docking a vessel offshore that reduces the time that the vessel is out of service. What is also needed is a method of dry-docking a vessel offshore without relocated the vessel or its cargo.